Tabletop bio-safty air curtain

ABSTRACT

A tabletop laminar flow HEPA filtered air curtain, for use as a bio-safety separation barrier for the personal protection of individuals from a respired aerosol, is provided. The air curtain has a rectangular cabinet. The cabinet is partitioned into a fan housing, in fluid communication, with a HEPA filter box. The fan housing has an air intake. A fan assembly is mounted in the fan housing. The fan assembly has a ducted housing, in fluid communication with the ambient air intake, and a blower. A horizontal HEPA filter is mounted in the filter box so that a blower discharge passes through the HEPA filter, and upwardly and uniformly through an elongated laminar flow nozzle in a top wall of the filter box.

CROSS REFERENCE TO RELATED APPLICATIONS Statement of Federally Sponsored Research

None.

TECHNICAL FIELD 1. Field of the Invention

The present invention relates to bio-safety separation barriers. In particular, it relates to a HEPA filtered tabletop laminar flow separation barrier for filtering, and redirecting a respired aerosol containing an infectious viral agent.

BACKGROUND OF THE INVENTION 2. Description of the Related Art

Aerosols are an important mode of transmission for infectious agents, such as Influenza and SARS COV2 (COVID-19) viruses. Several authors have reported that aerosol large-droplet transmission is the predominant mode by which the virus infection is acquired. As a consequence, various modes for protection of the public against infectious aerosols are recommended. In the context of COVID-19 pandemic preparedness, such recommendations include the practice of social distancing, and the use of various forms of bio-safety barriers. These barriers are referred to as items of personal protective equipment (PPE). PPE barriers include various forms of facial coverings worn by the individual in order to block the spread of respired large-droplet aerosols. The use of PPE has gained wide acceptance in the retail, business, food service, and beverage industries.

Aerosols are suspensions in air (or in a gas) of solid or liquid particles, small enough that they remain airborne for prolonged periods because of their low settling velocity. Coughing or sneezing generates a substantial quantity of particles, a large number of which are <5-10 μm in diameter. Humans acutely infected with COVID-19 virus have a high virus titer in their respiratory secretions, which will be aerosolized when the patient sneezes or coughs.

Settling times can be further affected by air turbulence. While the use of mask barriers, such as plastic face shields and fabric masks, reduces the volume of aerosol they have little to no effect on the settling velocity of a pathogenic aerosol in suspension. Moreover, they are typically removed by an individual when speaking, eating, and drinking in public places. These actions essentially defeat the efficacy of using a mask barrier form of PPE, in an indoor environment having a, very-low air turbulence. In these settings, it has been reported, that the settling time, for spherical particles, can be as high as 62 minutes, and that particles<0.5 μm may not settle at all.

A typical building design, will include an HVAC system sufficient to supply the room with a total refresh of air periodically. For example, in restaurants, the number of Air Changes Per Hour (ACH) is set by the standards organization ASHRAE to be 8-12 ACH. However, in many HVAC designs the position of the supply and exhaust are on the ceiling and the “air exchange” is neither uniform nor perfectly mixed. This configuration results in “pockets” of air that are refreshed much less often than specified, if at all. Thus, substandard designs provide a prime environment for stagnant localized air, and the potential for infectious vapors.

Air Curtains are used extensively in industrial applications to separate one volume of air from another. An air curtain works by directing a high-velocity air stream perpendicular to a “boundary” line, to prevent air and small particles on either side from crossing the boundary. Meanwhile, large objects can still cross, because their momentum is sufficient to cross the high velocity stream. For example, air curtains are often deployed in retail doorways to allow the entrance to be open to customers while simultaneously preventing insects from entering. Another application area is loading docks where overhead doors are open, and the air curtain is used to save energy by keeping some of the heat (or cool) inside the building. These units tend to be large and fit above door entrances blowing air downwards.

While the foregoing mask barriers forms of PPE offers some utility, what is needed is a barrier for the protection of the public, when speaking, ingesting food or beverage, engaging in retail transactions, or conducting business, in an indoor setting. The present invention satisfies these needs.

BRIEF SUMMARY OF THE INVENTION

Therefore, it is an objection of the present invention to provide a barrier to the spread of a large-droplet respired aerosol in a social setting.

It is another object of the present invention to reduce stagnant localized air in an indoor setting.

It is another object of the present invention to provide a table top air curtain barrier which is useful to block the spread of large-droplet aerosol particles when speaking, ingesting food or beverage, engaging in retail transactions, or conducting business, in an indoor setting.

It is another object of the present invention to provide a table top air curtain barrier for protecting individuals from a viral infection for prolonged periods using a high-efficiency-particulate filter medium, in combination with an upward laminar air flow.

It is another object of the present invention to provide a vertical air curtain to redirect vapors and remaining small particles that may be exhaled by persons on either side of the curtain, up into the air, thus reducing the probability of virus transmission from one person to another.

It is another object of the invention to provide a small “desktop” apparatus that filters localized air that is respired from a person to improve ambient air quality, over time.

It is another object of the present invention to provide a discharge of HEPA filtered air from a tabletop upwardly and vertically, at a high speed, creating a curtain of air being useful in creating a mask-less separation barrier between two people opposite of one another in a social or business setting, such as a food or beverage establishment, office, or retail counter.

It is yet another object of the present invention, to provide an air curtain having a high velocity air stream, and which creates an adjacent low-pressure area, on either side, which will cause surrounding air to be drawn toward the apparatus and subsequently, filtered and entrained in the upward air stream.

To overcome the problems of the prior art, and in accordance with the purpose of the invention, as embodied and broadly described herein, briefly a tabletop laminar flow air curtain is provided. The air curtain is a HEPA filtered air curtain barrier for the personal protection of individuals from a respired aerosol. The air curtain has a rectangular cabinet. The cabinet is a ducted construction having top, bottom, side and end-cap walls, and is partitioned into a fan housing, in fluid communication, with a HEPA filter box. The fan housing has at least one ambient air intake opening. A fan assembly is mounted in the fan housing. The fan assembly has a ducted housing in fluid communication with the ambient air intake. The ducted housing is adapted to redirect an aerosolized volume of the ambient air, in a specific direction, as a blower discharge air into a lower portion of the filter box. A horizontal HEPA filter is mounted above the lower portion of the filter box so that the blower discharge air is a filtered blower discharge air by passing upwardly through the HEPA filter, in the filter box. An elongated nozzle is formed in the top wall of the filter box. The nozzle has a gap being adapted to uniformly pass the filtered blower discharge air, as an upward vertical laminar flow curtain of air, so that a biosafety barrier is maintained between the individuals to be protected.

Additional advantages of the present invention will be set forth in part in the description that follows, and in part will be obvious from that description, or can be learned from practice of the invention. The advantages of the invention can be realized and obtained by the table top biosafety air curtain being particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The accompanying drawings, which are incorporated in, and which constitute a part of the specification, illustrate at least one embodiment of the present invention and, together with the description, explain the principles of the invention.

FIG. 1 is a tabletop view of the present invention showing the upward directional air flow and low pressure region for incoming ambient air with the air curtain.

FIG. 2 is an enlarged view of the tabletop air curtain, shown in FIG. 1.

FIG. 3 is an isometric exploded view, of the present invention, showing the hidden lines as dashed.

FIG. 4 illustrates two isometric sectional views, of the present invention, illustrated from opposite viewpoints.

FIG. 5 is an exploded isometric top view of the present invention, and a horizontal sectional view of the cabinet from a perspective of the filter box upper exhaust plenum.

FIG. 6 is an exploded isometric bottom view of the present invention, and the horizontal sectional view of the cabinet, shown in FIG. 5, from a perspective of the filter box lower discharge air plenum.

DETAILED DESCRIPTION OF THE DRAWINGS

Unless specifically defined otherwise, all technical or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

Although, any of the methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are now described. Reference will now be made in detail to the presently preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings wherein like numerals represent like features of the invention.

The present invention is a tabletop 28 apparatus 10, for use as a bio-safety barrier, and to circulate a stagnant air condition, in an indoor setting. The table top 28 apparatus 10 is also useful in sanitizing the recirculated air by filtering the circulated air. The apparatus 10 is particularly useful as a mask-less PPE apparatus for use as an upward vertical barrier against to the spread of infectious agents, such as SARS-COV2 (COVID-19). The apparatus 10 alters incoming aerosolized vapor being present in ambient room air, and directs a high pressure upward vertical air “curtain” 17 of air which functions as a sanitizing physical barrier being useful to in distancing opposing individuals, to be protected. The vertical air curtain 17 redirects those respired aerosol particles that may be exhaled by opposing persons, on either side of the curtain 17, upwards into the room HVAC system, as a barrier, and thereby reduces the likelihood of viral transmission from one person to another, in a social setting. In this manner, the apparatus 10 finds utility in food and beverage establishments, meetings, and in retail sales when masking is impracticable.

The apparatus has a rectangular cabinet 14. The cabinet 14 is a ducted construction having top, bottom, side 21 and end-cap walls, The cabinet 14 is partitioned into the fan housing 30, which is in fluid communication, with a HEPA filter box 20. Fluid communication is enabled via the exhaust duct 36 in the partition 37. The exhaust duct 36 and partition 37 create a back pressure. The fluid 11 is an aerosolized vapor, and is under a high pressure condition within the cabinet 14. The cabinet 14 is desirably of a ducted metal construction having a length, width and height being approximately 61 cm×30.5 cm×23 cm, respectively. The fan housing 30 has at least one ambient air intake opening 15, in the sidewalls 21. In the presently preferred embodiment, the fan housing includes a pair of intake openings in parallel and opposite alignment. The filter box 20 desirably includes a pair of inner horizontal filter rails 24 adapted to support a HEPA filter 26 above an upper margin of the exhaust duct 36.

A fan assembly is mounted in the fan housing 30. The fan assembly 32 includes a blower fan in a ducted housing. The blower fan is motor 33 driven. The motor is powered using conventional 120 VAC power, or any power supply being well accepted in the food, beverage, business, or commercial industries. The motor 33 is coupled with a switch for on/off discontinuous operation of the apparatus 10, according to the present invention. The blower fan may be of any type, which is well known in the art, but is desirably of a centrifugal type configuration having a number of fan impellers, or blades, in a cylindrical configuration. The aerosolized vapor 11 intake the fan assembly at the intake openings 15, is turned 90 degrees, and accelerates horizontally, due to centrifugal force, as it exits the fan housing through the exhaust duct 36 in the partition 37. The cylindrical, or tubular, construction of the fan assembly 32 creates a tubular open air intake in the fan assembly 32. Aerosolized large-droplet particles enter the fan assembly 32 through the air intake openings 15 in the fan housing 30.

In the presently preferred embodiment, the Centrifugal fan assembly 30 is a mechanical apparatus for moving air or other gases in a direction at an angle to the incoming fluid. The Centrifugal fan assembly 30 contains a ducted housing to direct outgoing air in a specific direction, horizontally across the HEPA filter 26 media interface. The fan increases the speed and volume of the air stream with the rotating impellers.

The Centrifugal fan assembly 32 uses the kinetic energy of the impellers to increase the pressure of the air stream, which in turn moves against the resistance caused by the exhaust duct 36, formed in the partition 37. The Centrifugal fan assembly 32 displaces the air radially, changing the direction (90°) of the airflow. In this manner, the present invention provides a sturdy, quiet, and reliable, upwards air curtain 17 barriers which is capable of operating over a wide range of conditions. In operation, the Centrifugal fan assembly 32 further generates a vacuum condition, in relation to the side walls 21, of the cabinet 14. This vacuum condition draws the aerosolized vapor 11 into the fan housing intakes 15.

The fan assembly 30 includes a ducted housing. The ducted housing is desirably a formed from a sheet of metal or polymer. The ducted housing circumscribes the centrifugal impellers, and is in fluid communication with the ambient air intakes 15. The ducted housing is adapted to redirect an aerosolized volume of the room air vapor 11, in a specific direction, as a blower discharge air into a lower portion of the filter box 20.

The filter box 20 includes a pair of horizontal filter rails 24 for removably supporting a horizontal high-efficiency particulate air (HEPA) filter 26. The HEPA filter 26 is designed to catch any particulate that is in the air during normal conversations between the two-opposing people, and clean the air while in use. The HEPA filter 26, is of any type which is well known in the art. The HEPA filter 26 desirably traps any particulate in the aerosolized vapor 11 being greater than 0.03 microns in size. The horizontal HEPA filter 26 is supported, spatially and horizontally, above the lower portion of the filter box 20, so that the blower discharge air is a filtered when passing upwardly through the HEPA filter 26. The HEPA filter 26 is desirably removable, and is intended to be replaced, periodically, according to manufacturer's recommendations. In the presently preferred embodiment, the HEPA filter 26 is 65 mm thick, with a surface area of about 0.470 m2. It is desirable that, in operation, the HEPA filter kinematic resistance is approximately 1e−06, a pressure drop of 0.56 mm mercury, with an inertial resistance being 8251 Pa.

In the presently preferred embodiment, the HEPA filter 26 is a composite construction being capable of filtering aerosolized large-droplet particulates, including biological viral pathogens, which may arise from a person respiring, sneezing or coughing, when seated opposite of another. These particulates, are typically ranging in size from 0.5 microns to 45.0 microns, and are drawn into the lower portion of the filter box 20 through lower pressure condition, which is adjacent to the side walls 21 of the cabinet 14, in operation of the Centrifugal fan assembly 32.

In operation, the filter box 20 functions, under high pressure, with a lower blower discharge plenum 23 (FIG. 6), and an upper, filtered air, exhaust plenum 22 (FIG. 5). The plenums are separated by the HEPA filter 26. The upper exhaust plenum is a pressurized exhaust for laminar flow discharge through an elongated nozzle 16 formation in the top wall of the filter box 20. The elongated nozzle 16 is functionally designed, with a gap, of a specific configuration, adapted to uniformly pass the HEPA filtered air, as an upward vertical laminar flow air plume, or curtain 17, to generate the biosafety barrier, between the individuals to be protected. It is desirably that the nozzle 16 be configured with a length in the range of 400-600 mm. In this manner, for a 432 mm nozzle 16 length, the presently preferred embodiment employs a 12.7 mm nozzle gap, operating at 100-160 Pa, to generate a constant 1.83M high HEPA filtered air plume, where the blower discharge is passing at 4 meters per second, passing, from the nozzle, uniformly. The result is an upward air curtain 17 that will provide the benefits of both deflecting any of the smaller vapors or gases typical in exhalation, as well as diverting the gaseous vapors from the cough or sneeze into the buildings HVAC system. Thus, it is apparent, from the above parameters that the desired nozzle gap is in a range of 11 to 14 millimeters, when operating at an air-flow-rate (Volumetric Flow Rate) in the range of 3 to 5 m³/s.

The tabletop 28 laminar flow air curtain 17, more desirably includes at least one grill 12 attached to an outside surface of at least one of the cabinet side walls 21. With the presently preferred embodiment, the grill 12 is configured as a removable pre-filter housing with a media filter 27 positioned, therein to separate larger non-aerosolized particles, such as dust, insects, and the like, from entering the air intake 15 of the fan housing 30. The media filters 27 are of any type which are well known in the art, but may be constructed using a cellulose or polymer substrate with, or without, an activated carbon layer. In the presently preferred embodiment the media filters 27 are a pre-filter configured to generate a pressure drop of less than, or equal to, 0.15 mm mercury. The grill 12 includes a series of air intake openings 13. In operation, the aerosolized vapor 11, redirected as a result of the negative pressure condition, enters the grill 12 through the series of air intake openings 13, passes through the media pre-filter 27, and travels, tangentially, along, and adjacent to, the cabinet side walls 21, into filter box intake opening 15, and into the fan assembly 32 for discharge, by passing through the exhaust duct 36, into the lower portion of the HEPA filter box 20. In operation, the media pre-filters 27 are more desirably configured to generate a kinematic resistance being 1e−06, and an inertial resistance of 6525 Pa.

Additional advantages of the present invention will be set forth in the description that follows, and in part will be obvious from that description or can be learned or appreciated from practice of the invention. Moreover, the advantages of the invention can be realized and obtained by the invention as more particularly pointed out in the appended claims. 

I claim:
 1. A tabletop laminar flow air curtain of for the protection of individuals from a respired aerosol, comprising: (a) a rectangular cabinet, of a ducted construction, having top, bottom, side and end-cap walls, wherein said ducted construction is partitioned into a fan housing in fluid communication with a HEPA filter box; (b) at least one ambient air intake opening in said fan housing; (c) a fan assembly, mounted in said fan housing, including a ducted housing being in fluid communication with said air intake, and adapted to redirect an aerosolized volume of said ambient air, in a specific direction, as an blower discharge air into a lower portion of said filter box; (d) a horizontal HEPA filter mounted above said lower portion of said filter box so that said blower discharge air is a filtered blower discharge air, by passing upwardly through said HEPA filter, in said filter box; and (e) an elongated nozzle in said top wall of said filter box having a gap being adapted to uniformly pass said filtered blower discharge air as a vertical laminar flow curtain of air so that a biosafety barrier is maintained between the individuals to be protected.
 2. The tabletop laminar flow air curtain according to claim 1, further comprising at least one grill attached to an outside wall of at least one of said side walls.
 3. The tabletop laminar flow air curtain according to claim 1, wherein the fan is a centrifugal fan.
 4. The tabletop laminar flow air curtain, according to claim 2, wherein the grill is a removable filter housing, and further comprising a media filter positioned in said removable filter housing.
 5. The tabletop laminar flow air curtain, according to claim 3, wherein the nozzle gap is in a range of 11 to 14 millimeters and the velocity of the filtered blower discharge an air-flow-rate in the range of 3 to 5 meters per second.
 6. The tabletop laminar flow air curtain, according to claim 3, wherein the tabletop laminar flow air curtain has a Volumetric Flow Rate in the range of 0.02 to 0.05 m3/s.
 7. A method for using of a tabletop laminar flow air curtain, as a bio-safety separation barrier, for the protection of individuals being seated oppositely from one another, from a large droplet respired aerosol transmission of a viral agent, comprising the steps of: (a) Providing a rectangular cabinet, of a ducted construction, having top, bottom, side and end-cap walls, wherein said ducted construction is partitioned into a fan housing in fluid communication with a HEPA filter box; (b) Providing at least one ambient air intake opening in said fan housing; (c) Providing a fan assembly, mounted in said fan housing, including a ducted housing being in fluid communication with said air intake, and adapted to redirect an aerosolized volume of said ambient air, in a specific direction, as an blower discharge air into a lower portion of said filter box; (d) providing a horizontal HEPA filter mounted above said lower portion of said filter box so that said blower discharge air is a filtered blower discharge air, by passing upwardly through said HEPA filter, in said filter box; (e) providing an elongated nozzle in said top wall of said filter box having a gap being adapted to uniformly pass said filtered blower discharge air as a vertical laminar flow curtain of air so that a biosafety barrier is maintained between the individuals to be protected; (f) positioning the bottom wall of the rectangular cabinet on a tabletop between the seated individuals to be protected; and (g) powering the fan assembly wherein the individuals to be protected are separated by the bio-safety separation barrier.
 8. The method according to claim 7, further comprising, the steps of providing at least one grill attached to an outside wall of at least one of said side walls.
 9. The method according to claim 7, wherein the fan is a centrifugal fan.
 10. The method according to claim 7, wherein the viral agent is an RNA virus.
 11. The method according to claim 9, wherein the grill is a removable filter housing and further comprising, the step of providing a media filter positioned in said removable filter housing.
 12. The method according to claim 9, wherein the nozzle gap is in a range of 11 to 14 millimeters and the velocity of the filtered blower discharge air is at an air-flow-rate in the range of 3 to 5 meters per second.
 13. The method according to claim 9, wherein the tabletop laminar flow air curtain has a Volumetric Flow Rate in the range of 0.02 to 0.05 m3/s.
 14. The method according to claim 9, wherein the centrifugal fan generates a pressure in the range of 150-250 Pa.
 15. The method according to claim 9, wherein the centrifugal fan generates a suction velocity inlet boundary condition measured at an outer surface of the media filter 3-6 m/s and a discharge velocity condition measured at the nozzle in the range of 3-6 m/s.
 16. The method according to claim 9, wherein the HEPA filter is 65 mm thick. 